The present invention relates to a photogalvanic cell, which is in particular usable for converting solar energy into electrical energy.
For a number of years research has been carried out in connection with devices making it possible to recover solar energy in the form of thermal or electrical energy. As a result of this research photogalvanic cells have been developed which make it possible to convert light energy from the sun into an electromotive force. These cells comprise two electrodes placed in a liquid containing one or more redox systems, including a photosensitive type constituted, for example, by a dye or stain such as thionine. In these cells one of the electrodes is illuminated by a light beam, whilst the other electrode remains in the dark. The absorption of the visible radiation by the photosensitive type makes it possible to produce redox reactions in the liquid, which give rise to the appearance of a potential difference at the electrodes of the cell. As a result they can supply electrical current without consuming the various constituents of the liquid or the electrodes. When the photosensitive type is thionine, the liquid conventionally contains a redox relay system constituted either by Fe.sup.2+ /Fe.sup.3+, or by an organic constituent such as hydroquinone.
However, such cells do not make it possible to obtain satisfactory conversion efficiencies. Thus, the voltages obtained are generally below 300 mV and the power levels obtained are at the most a few dozen .mu.watts/cm.sup.2. Moreover, when the relay system is in an organic constituent the liquid loses it stability after a few minutes. Conversely, with relay systems constituted by Fe.sup.2+ /Fe.sup.3+ good stability is obtained, but then the power of the cell does not exceed 1 .mu.W/cm.sup.2.